1. Field of the Invention
The present invention relates to an inkjet cartridge for use in an inkjet recording apparatus.
2. Description of the Related Art
In an inkjet recording system, ink droplets are ejected from discharge ports (also referred to as nozzles) provided in a recording head toward a recording medium so as to achieve recording. Ink is stored in an ink tank integrally or separately provided in the recording head. The ink contained in the ink tank is supplied to the recording head via an ink supply opening provided in the ink tank.
Regardless of whether the ink tank is integrated with the recording head or separate therefrom, a plurality of ink reservoirs (also referred to as ink chambers or simply chambers) may be provided within the ink tank. With an increasing number of ink reservoirs, the size of the ink tank or recording head needs to be increased. However, there is a limitation on the size in a space in the recording apparatus where the ink tank or the recording head is mounted. On the other hand, in order to increase the number of ink reservoirs without increasing the size of the ink tank or the recording head, the volume of each of the ink reservoirs has to be reduced. However, the reduction in volume of the ink reservoir may cause more frequent tank replacement.
In U.S. Pat. No. 4,771,295, a multi-chamber inkjet recording head is disclosed, in which ink chambers are arranged in parallel with each other. In U.S. Pat. Nos. 5,926,195 and 6,260,961, a structure is disclosed, in which a first chamber and a plurality of other chambers juxtaposed along the side wall of the first chamber are arranged. In these structures, the first chamber is arranged in the vicinity of the nozzle corresponding thereto, so that ink flow paths from a plurality of the juxtaposed chambers to the first chamber are reduced in length and simplified in structure.
However, in the structure disclosed in U.S. Pat. No. 4,771,295, there have been the following problems. That is, when the ink tank has three or more ink chambers and these ink chambers are linearly arranged, the length of the ink flow path from the remote ink chamber to the nozzle is relatively increased. If the length of the ink flow path is elongated, dust and bubbles are liable to be mixed, elevating the incidence rate of ejection failure or non-ejection. If a plurality of ink chambers with different lengths is mixed, a problem also arises in that the flow path design is complicated. The entire length of such flow paths has to be filled with ink, so that wasteful ink is increased. Since the length and shape of each ink flow path are different, the flow resistance may become nonuniform in the ink flow path. Additionally, entirely juxtaposing a plurality of ink chambers makes the recording head width wide, resulting in less convenience for handling.
On the other hand, in the structures disclosed in U.S. Pat. Nos. 5,926,195 and 6,260,961, there have been the following problems. That is, in comparison with the first chamber, the flow path length to the nozzle of a plurality of the other chambers juxtaposed is also elongated so that the ink flow path length cannot be also uniformed. The arrangement and the flow path design are complicated in the same way as in the structure disclosed in U.S. Pat. No. 4,771,295. Furthermore, when the number of ink flow chambers is four or more, the flow path length between the most remote chamber from the nozzle and the nozzle becomes very long in comparison with that between the first chamber and the nozzle, so that the effect is scarcely expected.